The case for dual domestication of vitis vinifera, as per Dong, et al.

The recent Dong, et al., study has upended the conventional wisdom of a single-point vitis vinifera domestication somewhere in the Caucasus over 8000 years ago. In a series reporting on the study, I have specified the study origin and the history of vitis sylvestris, the accepted progenitor of vitis vinifera. In this post I cover the study findings as regards the domestication of vitis vinifera.

Vitis vinifera sylvestris (Source: floredusud.com)

According to the Dong, et al., study, the wet climate of the Early Holocene (11,700 - 8300 years ago) expanded the geographic spaces capable of sustaining Syl-E (identified in my prior post as the eastern ecotype of v. sylvestris) and the species rose to the occasion by moving westward, occupying a "large geographic space from Central Asia to the Iberian Peninsula."

I have identified six genetic ancestries for cultivated grapes reported out in the Dong, et al., study -- CG1 to CG6 -- each associated with a specific geographic area. For example, CG1 is associated with Western Asian table grapevines and CG2 with Caucasian wine grapevines. CG1, according to the study, "shares the main ancestral components with Syl-E1" while CG2 shares its main components with Syl-E2. This state of affairs suggests the possibility of two domestication events. Further:

• CG1 and CG2 maintain the highest genetic diversity of all the CG groups
• CG1 and CG2 manifest the greatest Linkage Disequilibrium decay among all CG groups
• CG1 and CG2 are less differentiated from their corresponding wild ecotypes
• The Akaike information criterion-based phylogenetic selection prefers a dual origin tree model which agrees that CG1 and CG 2 are genetically closer to Syl-E1 and Syl-E2, respectively
• The population split lines of CG1/Syl-E2 and CG2/Syl-E1 pairs resemble that of Syl-E1/Syl-E2 and differ from those of CG1/Syl-E1 and CG2/Syl-E2 pairs.

These data, according to the study, "collectively support a dual origin of v. vinifera and reject the theory of a single primary domestication center."

Both sylvestris/cultivar pairs (CG1/Syl-E1 and CG2/Syl-E2) separated quickly which, according to the authors, is compatible with a "clean-split" scenario. The authors estimate the median population split time to be ~ 11,000 years ago for both pairs "suggesting that the domestication events took place concurrently around the advent of agriculture."

In that CG1 represents the Western Asian table grapevine, and CG2 the Caucasian wine grape vine, the dual-origin schema advanced herein rejects earlier assumptions that wine grape domestication predated table grape domestication. To reiterate, the data suggest vitis vinifera simultaneous origins in Western Asia and the Caucasus, covering both wine grapes and table grapes.

The implications of the foregoing are mind-blowing. It suggests that Syl-E1 and Syl-E2 had self-selected for characteristics that rendered one more palatable as a food source and the other as a beverage. Further, it means that hunter-gatherers within the regions had been interacting with these ecotypes in their natural habits and habitats for many years prior to the instance of dual selection and propagation of the characteristics embodied in CG1 and CG2.

My next post will highlight how domesticated grapes spread from these points of origin to the major wine regions.

©Wine -- Mise en abyme